misc: cxl: use kobj_to_dev()

BugLink: http://bugs.launchpad.net/bugs/1588468

Use kobj_to_dev() instead of open-coding it.
Signed-off-by: Geliang Tang <geliangtang@163.com>
Reviewed-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 85016ff3)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

drivers/misc/cxl/sysfs.c

@@ -396,8 +396,7 @@ static ssize_t afu_eb_read(struct file *filp, struct kobject *kobj,
 			       struct bin_attribute *bin_attr, char *buf,
 			       loff_t off, size_t count)
 {
-	struct cxl_afu *afu = to_cxl_afu(container_of(kobj,
-						      struct device, kobj));
+	struct cxl_afu *afu = to_cxl_afu(kobj_to_dev(kobj));
 
 	return cxl_afu_read_err_buffer(afu, buf, off, count);
 }
@@ -477,7 +476,7 @@ static ssize_t afu_read_config(struct file *filp, struct kobject *kobj,
 			       loff_t off, size_t count)
 {
 	struct afu_config_record *cr = to_cr(kobj);
-	struct cxl_afu *afu = to_cxl_afu(container_of(kobj->parent, struct device, kobj));
+	struct cxl_afu *afu = to_cxl_afu(kobj_to_dev(kobj->parent));
 
 	u64 i, j, val;